One of the main discoveries in metals research in the last 20 years involves the strengthening due to nanosized clusters. In many metal alloys with two or more alloying elements strengthening is predominantly caused by so-called co-clusters. Research in Southampton on these co-clusters through a series of projects has been led by Prof Marco J Starink.
Co–clusters are nanoscale aggregates in ternary or higher order alloys containing 2 types of alloying elements. Whilst initial work at Southampton focussed on the effects of modulus hardening recent work has established that the bond energy between the solute atoms is the main component in the strengthening effect. In work published in 2009 (Starink and Wang, Acta Mater, 57, 2376) a model for the thermodynamics of co-clusters and their strengthening was presented, and the model was applied to predict co-cluster formation and strengthening in Al based alloys. In recent years the model has been further expanded to include a range of other alloys.
Co–clusters are nanoscale aggregates in ternary or higher order alloys containing 2 types of alloying elements. Whilst initial work at Southampton focussed on the effects of modulus hardening recent work has established that the bond energy between the solute atoms is the main component in the strengthening effect. In work completed in 2010 a model for the thermodynamics of co-clusters and their strengthening was presented, and the model was applied to predict co-cluster formation and strengthening in Al based alloys. In recent years the model has been further expanded to include a range of other alloys.
Images on the right show possible constellations of co-clusters in an fcc lattice (from the top): a dimer, a 4 atom cluster, a two atom co-cluster at next nearest neighbour position
